Line Head and Image Forming Apparatus

Abstract

A line head includes light-emitting elements arranged in a first direction; and an optical system that images light emitted from the light-emitting elements on a latent image carrier. The optical system including first and second lens surfaces having refractive power, the second lens surface being provided on a side of the first lens surface opposite to the light-emitting elements. In cross sections in the first and second directions including an optical axis of the optical system, the curvatures of the first and second lens surfaces satisfy the following relationships: |C 1X |<|C 1Y |; and |C 2X |>|C 2Y | where, |C 1X | and |C 2X | are absolute values of the curvatures on the optical axis of the first and second lens surfaces on the cross section in the first direction, respectively; and |C 1Y | and |C 2Y | are absolute values of the curvatures on the optical axis of the first and second lens surfaces on the cross section in the second direction.

1 . A line head comprising:
 light-emitting elements arranged in a first direction; and   an optical system that images light emitted from the light-emitting elements on a image surface, wherein:   the optical system is provided with:   a first lens surface having refractive power; and   a second lens surface having refractive power that is provided on a side of the first lens surface opposite to the light-emitting elements; and   in a cross section in the first direction including an optical axis of the optical system and a cross section in a second direction including the optical axis, the second direction being orthogonal to the cross section in the first direction, the curvatures of the first and second lens surfaces satisfy the following relationships:
   | C   1X   |<|C   1Y | 
   | C   2X   |>|C   2Y | 
   where, |C 1X | is the absolute value of the curvature on the optical axis of the first lens surface on the cross section in the first direction;   |C 2X | is the absolute value of the curvature on the optical axis of the second lens surface on the cross section in the first direction;   |C 1Y | is the absolute value of the curvature on the optical axis of the first lens surface on the cross section in the second direction; and   |C 2Y | is the absolute value of the curvature on the optical axis of the second lens surface on the cross section in the second direction.   
     
     
         2 . The line head according to  claim 1 , wherein the optical system includes a first lens having the first lens surface and a second lens having the second lens surface. 
     
     
         3 . The line head according to  claim 2 , wherein the first lens has a flat surface on an opposite side to the first lens surface. 
     
     
         4 . The line head according to  claim 3 , wherein the first lens surface of the first lens opposes the light-emitting elements. 
     
     
         5 . The line head according to  claim 1 , wherein an aperture diaphragm is provided close to a front-side focal plane of the optical system. 
     
     
         6 . An image forming apparatus comprising:
 a latent image carrier on which a latent image is formed; and   a line head that performs exposure on the latent image carrier so as to form the latent image, wherein   the line head comprises:   light-emitting elements arranged in a first direction; and   an optical system that images light emitted from the light-emitting elements on a latent image carrier, wherein:   the optical system is provided with:   a first lens surface having refractive power; and   a second lens surface having refractive power that is provided on a side of the first lens surface opposite to the light-emitting elements; and   in a cross section in the first direction including an optical axis of the optical system and a cross section in a second direction including the optical axis, the second direction being orthogonal to the cross section in the first direction, the curvatures of the first and second lens surfaces satisfy the following relationships:
   | C   1X   |<|C   1Y |; and 
   | C   2X   |>|C   2Y |, 
   where, | 1X | is the absolute value of the curvature on the optical axis of the first lens surface on the cross section in the first direction;   |C 2X | is the absolute value of the curvature on the optical axis of the second lens surface on the cross section in the first direction;   |C 1Y | is the absolute value of the curvature on the optical axis of the first lens surface on the cross section in the second direction; and   |C 2Y | is the absolute value of the curvature on the optical axis of the second lens surface on the cross section in the second direction.